Dr Gunnar Mallon

University Teaching Assistant

Gunnar Mallon received a BSc (First Class Honours) in Environmental Science from the University of Stirling in 2007 and a PhD in Palaeoecology (entitled: Patterns of mid-Holocene climate change – evidence from the peat archive) from the University of Southampton in 2012. From 2010 to 2013, Gunnar worked as PDRA on the NERC-funded PRECIP project at the University of Southampton, investigating Holocene climate change in Atlantic Canada and Maine.

He started his post at Sheffield in February 2013.

Research interests

Impacts of changes in permafrost on ocean fertilisation.

The biogeochemistry and ecological evolution of Arctic wetlands with regards to changes in the depth of the active layer are key research priorities, as many cascading system are influenced by these changes. The ocean is a large driver in global climate and its contribution to greenhouse gas emissions is often neglected in large-scale climate models. My work focuses on understanding biogeochemical and hydrological changes on a landscape-scale of Arctic permafrost regions and their link to ocean fertilisation.

Wetland in Adventdalen, Svalbard (Photo: G. Mallon)

Reconstruction of natural climate variability (palaeoclimatology)

In order to make sense of our current climate and to gauge the influence that we, as a species, are having on the system, we need to understand natural climate variability. Reconstructing natural climate change and climate cycles allows us to establish relatively short-term trends in the climate system. I use testate amoebae, plant macrofossils, pollen, radiocarbon dating, tephrochronology, and stable isotopes (O, H, and C) in order to build up a model of what we would expect the climate to do without any anthropogenic disturbance.

Testate amoebae are single cell organisms that live on the water film, which forms on the leaves of bog mosses (Sphagnum). With over 20 generations per year, testate amoebae respond very quickly to changes in their environment. Understanding their modern ecological preferences, allows us to use them in a palaeo setting in order to reconstruct past climates and environments. However, there are still many questions regarding the ecological niches occupied by different testate amoebae species. My research focuses on a handful of species (e.g. Difflugia pulex) in order to understand their habitat preferences.

According to Viking Saga, Leif Erikson, son of Eric the Red, discovered Vinland (Newfoundland) when his boat was blown off-course during his travels from Iceland to Greenland. He consequently established an encampment at L’Anse Aux Meadows on the Northern Peninsula of Newfoundland, which served as a maintenance and restocking settlement. Iron ore was smelted at L’Anse Aux Meadows and transported back to Greenland along with charcoal. However, the settlement was only occupied for a brief period and my research aims to answer the questions if climatic factors were responsible for the abandonment of L’Anse Aux Meadows.

Current research

With changes in the depth of the active layer and geochemical processes, there is large uncertainty as to the concentration of nutrients flowing into the Arctic Ocean. The international LowPerm project, led by Prof. Andy Hodson (Geography), brings together partners from the UK, Norway, Denmark, and Russia in order to quantify biogeochemical fluxes on a landscape scale and to determine effects on ocean productivity.

Open pingo landform in Adventdalen with drainage (and reindeer) in the background (Photo: G. Mallon)

New Zoo – NOAH initiative

Part of a cross-faculty working group, led by Prof. Steve Banwart (Kroto Research Institute), we aim to set up an Environmental Observatory at a wetland owned by the Yorkshire Wildlife Park (YWP) in Doncaster. The Observatory will be the only depositional wetland in a global network of Critical Earth Observatories supported by the American, Chinese, French, German, and UK research councils. The observatory will provide a great teaching and research environment as well as providing invaluable outreach information for YWP.

Image Source: YWP

Environmental history of Adventdalen, Svalbard

Previous work in Adventdalen, Svalbard, has shown peat formation to date back 3.5k years. Given the large-scale environmental changes experienced in the Arctic during the Holocene, the peat deposits in Adventdalen are an ideal proxy source of palaeoenvironmental and palaeoclimatic information. A combination of pollen, testate amoebae, and plant macrofossil analysis will provide clues into the environmental history of Spitsbergen.

Ecology of testate amoebae - the link between wetland geochemistry and testate amoebae

Testate amoebae are a very useful indicator of past bog surface wetness, as these respond very quickly to changes in the depth of the water table. However, their usefulness as indicators of geochemical parameters, in addition to hydrological parameters, still remains largely unexplored. Focussing on a number of key species, I aim to establish a link between physical and chemical parameters of a range of peatlands (minerotrophic and ombrotrophic) and the ecological preferences of testate amoebae living on them.

Holocene palaeoclimatic changes in the Atlantic provinces of Canada and Maine, USA

The climate of eastern Canada is closely linked to the balance between the Gulf Stream and the Labrador Current, producing a strong north-south climatic gradient. The PRECIP project aims to reconstruct this climatic gradient in order to make inferences about the strength of the respective ocean current throughout the Holocene. A combination of palaeoecological, chronological, and geochemical techniques are being employed to untangle the unique climatic and environmental history of the region.

Teaching

Gunnar convenes and lectures on a range of practical and theoretical undergraduate and postgraduate modules from the Geography and Environmental Science curricula as well as the PAC and ID masters programmes.